Children having Attention Deficit Disorder with Hyperactivity (ADD/HA) frequently show concomitant developmental learning disorders. Methylphenidate (MP) (Ritalin) is commonly prescribed for ADD/HA but its effects on classroom learning remain inadequately studied. Recent research on laboratory measures of learning suggest that achievement may be facilitated by doses of MP which are sub-optimal for behavior control. The present study seeks to determine, in children receiving a dual diagnosis of ADD/HA and Developmental Reading Disorder (DRD), a) whether MP can facilitate reading achievement, and b) whether MP's facilitation of reading achievement varies with drug dose. Children will be randomly assigned with restrictions to one of four drug treatment conditions (placebo, 0.3 mg/kg MP, 0.5 mg/kg MP, 0.7 mg/kg MP) and provided with 6 mo. of reading therapy using the Integrated Skills Method (ISM) -- a field tested and validated method for teaching reading skills. Possible differential dose effects of MP on reading achievement and classroom behavior will be assessed at 3 mo. and 6 mo. using measures of reading achievement, instruction process indices, social behavior, and learning-related performance. MP plasma levels will also be examined for their possible association with reading achievement and behavior change.